Obtain a SendGrid API key with Email Validation permissions from the SendGrid dashboard and store it as an environment variable SENDGRID_API_KEY.
POST the email address to the SendGrid email validation endpoint (v3/validations/email) with the source parameter set to describe the context (e.g., 'signup').
Parse the synchronous response: the verdict field returns 'Valid', 'Risky', or 'Invalid'; additional fields include checks for format, domain, local part, and additional properties such as disposable or role-based classification.
Use the verdict and checks to decide whether to accept the email at registration: block 'Invalid', optionally flag 'Risky' for further review, and accept 'Valid'.
Log the validation result alongside the user's email for audit purposes; re-validate on significant events such as email change.
Do not use email validation as the sole identity signal; combine it with other risk signals in your onboarding stack.
Known gotchas
Email validation is a paid Twilio SendGrid add-on and requires a Pro plan or higher; confirm your plan includes access before integrating.
The API validates format, DNS, and heuristic signals but cannot guarantee deliverability with certainty; treat results as risk signals, not hard truth.
Disposable or temporary email addresses are flagged under the checks object; decide your policy on disposable emails before surfacing the block to users.
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